Engine performance problems are typically caused by the failure or diminished operation of a single control system or single engine cylinder. Many conventional diagnostic instruments are designed for testing or troubleshooting various systems, including the ignition, induction, electrical, and emissions systems. One problem with conventional diagnostic instruments is that they often require complicated or time-consuming connections to the engine. Further, conventional diagnostic instruments may display results that are difficult to interpret or provide only general information. That is, a technician may invest time setting up a diagnostic instrument yet not receive specific enough information about a problem or performance issue to perform a repair efficiently.
In a properly functioning reciprocating engine, each cylinder contributes equally to the total output power for balanced operation. A lack of equal contribution to overall power typically produces an imbalance in the form of an unwanted engine block motion. That is, the lack of expected contribution from one or more cylinders can cause the engine to “rock” or displace with respect to the engine's normal, balanced motion on its mount points.
To evaluate engine cylinder contribution issues, typical diagnostic instruments infer the velocity of engine block movement from other measurements. One conventional technique measures the rate of change of alternator ripple and relates this to engine block movement.
One problem with inferring the velocity of engine block movement is the inaccuracy of the resulting information. In a typical belt-driven alternator system, for example, the belt does not move exactly with the engine. This makes it difficult to infer the engine block movement accurately from the alternator output current. Given that a performance problem is likely attributable to a malfunction of a single engine cylinder, a technician does not want to receive inaccurate information and, therefore, consume diagnostic or repair time on a properly functioning cylinder.
Additionally, common diagnostic instruments for evaluating an engine cylinder contribution may require the use of many pieces of equipment. For each piece of equipment, the technician must spend time setting it up and running the tests. Thus performing a comprehensive diagnostic test may require significant diagnostic time to localize or to pinpoint the specific trouble area.
What is needed is a diagnostic instrument for evaluating engine cylinder contribution that uses direct observation of engine block movements to provide specific results in an easily understandable manner.